RESEARCH:

Battery powered by humid air shows promise in lab

Jenny Mandel, E&E reporter

Greenwire: Tuesday, September 28, 2010

Anyone familiar with summer lightning might suspect a link between humid air and electricity. Now the research of a Brazilian scientist shows humidity creates an electrostatic charge that might be harnessed to make simple batteries or to prevent lightning from forming.

"Our research could pave the way for turning electricity from the atmosphere into an alternative energy source for the future," said study leader Fernando Galembeck of the University of Campinas in São Paulo, Brazil, in a description of his work. "Just as solar energy could free some households from paying electric bills, this promising new energy source could have a similar effect."

Last month, Galembeck presented a paper in Boston at the American Chemical Society's annual meeting, showing that a simple battery acquired an electrical charge as researchers ramped up the ambient humidity to which it was exposed.

In an interview, Galembeck said the battery -- composed of alternating layers of paper-like cellulose fibers and thin sheets of metal similar to aluminum foil -- developed a top charge of 0.8 volts. That is roughly half the 1.5-volt charge of a typical AA-type battery.

In his lab, a charge formed at humidity levels above 70 percent and got stronger as the level increased, Galembeck said. He has called the effect "hygroelectricity," meaning "humidity electricity."

The battery's total power is low, just a tiny fraction of the power of those in common use, and Galembeck said more work is needed to look at different materials and performance factors.

Its importance, he said, lies in its novelty and potential for widespread use. Batteries formed in this way could be used to provide energy in naturally occuring humid environments, or in the steamy conditions that quickly occur when water is placed in a closed environment like a plastic bag.

Another use he has suggested is that devices built on the principle could drain hydrostatic energy out of the air, preventing the build-up of energy that leads to lightning forming.

"I find it very curious that even though the connection between humidity and electricity in the atmosphere is very clear -- just watch a thunderstorm for this connection -- it has not been scientifically described, nor applied," Galembeck said. "The whole story is new."

He said the mechanism by which atmospheric electricity is formed and discharges is not clear, even 200 years after Benjamin Franklin's famed experiment with the key, the kite and the storm. Galembeck's belief is that whenever water evaporates or condenses, it does not remain neutral in charge but forms some positive and negative ions, he said.

Galembeck's presentation to some of the top chemical scientists in August received a range of reviews.

"I think it was very enthusiastic by many persons, very skeptical by many others, and a few seemed to be frankly outraged," he said.

Galembeck's lab took about a year to complete the experiments, he said, slowed down in part by the novelty of the results and the need to carefully eliminate other possible explanations for the charge the scientists found. He hopes other scientists will seek to replicate and validate the work.

"I hope it will progress fast, for a simple reason: I am not a young person," he said, noting that at 67, he is close to retirement. But he drew an analogy to studies of solar photovoltaic energy.

"Solar energy, when it started, the efficiency was very, very low. And even now, after many years of research, it is in very good devices up to 20-some percent, and [only] now they are really becoming practical," he said. "But the phenomenon, the basic phenomena, [have been] known for one century. So I think that that is the perspective you have to have."

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